The subject matter disclosed herein relates to a system for controlling a multilevel flying capacitor soft switching resonant power converter and optionally also to a system utilizing multiple modulation strategies to provide improved performance of the power converter over a broad range of operating conditions.
As is known to those skilled in the art power converters allow for a controlled output voltage and/or current to be supplied from an input power source. The input power source is a Direct Current (DC) supply which may have a fixed or variable amplitude. The controlled output voltage is an AC voltage and may have a variable amplitude and frequency (AC voltage). Numerous configurations of one or more active or passive switching devices along with inductive or capacitive devices are arranged to provide the controlled output voltage.
A common method for controlling the power converter utilizes “hard” switching. Hard switching requires turning an actively controlled switching device on or off at a desired time without consideration of the current or voltage being conducted by the switch. As a result, spikes in voltage and/or current result during the transitions between on and off. These spikes generate wide band electromagnetic noise as a function of the switching frequency. In addition, the switching devices incur switching losses due to the voltages and/or currents present during reverse recovery of the switching device.
Recent developments in power converters attempt to mitigate the switching losses and noise generated from “hard” switching by implementing “soft” switching. In soft switching, the switching devices are controlled to turn on and off when either the current or the voltage across the switching device is at or near zero. In super resonant inverter topology, the switching device is typically turned off when zero voltage, but some current, is present. A snubber capacitor is connected in parallel across each switching device which quickly removes the remaining current across the switching device after it has been turned off. As a result, a soft switching converter reduces the switching losses and noise generated when compared to a hard switching converter.
As is known, performance of resonant power converters may typically be optimized at one operating point. However, performance diminishes over a wide range of input voltages, load variations, or a combination thereof.
Thus, it would be desirable to provide a resonant converter exhibiting desired performance over a wide range of operating conditions.